This invention relates generally to the field of hand held soldering/desoldering tools and, more particularly, to such instruments which utilize a stream of gas to convey heat from its source along at least a portion of the path to the soldering point, the term "hand held" being intended to include robotic or robot-like applications. The term "gas" as used here usually means ambient air, but may include inert or relatively inert gases such, for example, as carbon dioxide or nitrogen or the noble gases or the like as when oxidation, corrosive reactions, or other undesired chemical action is to be minimized.
The advantages of hot gas soldering have become known and understood in recent years and are discussed in detail in Applicant's U.S. Pat. No. 4,926,028 co-pending application Ser. No. 47,771 filed May 8, 1987, the original parent case of which was Ser. No. 471,097 filed Mar. 1, 1983 and now abandoned. Both applications were entitled "Hot Air Soldering Instrument". It suffices here to point out that hot gas soldering by a stream of very hot gas with a very small cross section can apply precisely the desired quantity of heat at precisely the desired work point without deleteriously heating other adjoining or contiguous material or objects. In addition, the gas stream presents to the work point a substantially constant temperature heat source--unlike a conventional soldering tip the temperature of which inherently varies somewhat as varying amounts of heat are drawn therefrom and then replenished along a metal conduction path. A related advantage is that the gas may be heated instantly as it flows across, in heat exchange relation, the heat source and is instantly applied to the work point while a conventional soldering tool, exhibiting a significantly greater degree of thermal inertia, requires that heat be conducted through the solid components of the tool until the tip, inherently at some distance from the source, reaches a temperature adequate for working.
It may also be pointed out that by hot gas techniques, a thinwalled, low inertia soldering tip may be heated on its inside by an internally directed stream of hot gas providing most of the above advantages. In addition, although the soldering action is more like conventional soldering, the tip may be very desirably of iron composition since copper is not needed for its high thermal conductivity. Thusly avoided are the weight and expense of copper and its plating as well as its high vulnerability to decay by chemical reactions aggravated by its intense thermal environment.
These and other advantages of hot gas soldering have not been achieved in the prior art because of the difficulty of generating the gas stream, satisfactorily heating it, and providing means for shaping it and directing it upon the work point.
It is accordingly an object of the present invention to provide a hot gas soldering system which exhibits all these advantages of hot gas techniques.
It is another object to provide such a system which substantially instantly generates and applies to a work point a hot gas stream of predetermined cross section at a temperature of the order of 1500 degrees Fahrenheit and with a predetermined desired rate of heat energy flow to the work point.
It is another object to provide such a system in which the gas supply to the soldering instrument may be somewhat preheated by the electrical conductors conveying power to the heating element and in which the soldering instrument handle is cooled by the flow therethrough of the gas.
It is another object to provide gas heating apparatus for such a system which is exceedingly effective and efficient in supplying a very high temperature stream of air for soldering.
It is another object to provide such a system which is structurally simple, reliable, mechanically rugged, and inexpensive to manufacture.
It is another object to provide such a system in which the temperature of the heating element is electronically controlled remotely from the body of the soldering instrument itself.